This invention generally relates to an electrostatic painting system and method and more particularly, to an electrostatic painting system and method that accurately detects ground failures in portions of products or vehicles that are being painted.
During the manufacture of products, such as automotive vehicles, the products or vehicles are individually painted in a desired manner by use of a particular painting process, method and/or system. One type of painting process or system, commonly referred to as a high voltage electrostatic painting process or system, utilizes electrically charged paint particles to improve the efficiency and quality of the painting process. In this type of painting process, the product or vehicle to be painted is xe2x80x9cgroundedxe2x80x9d (e.g., is coupled to an electrical ground potential) and/or is attached to a grounded fixture. The product or vehicle is sent through one or more painting booths which selectively apply coats of paint to the product or vehicle. The paint is electrostatically charged at a relatively high voltage prior to atomization. Once the paint is discharged or atomized, the charged paint particles are xe2x80x9cdrawnxe2x80x9d or attracted to the grounded vehicle or product by electrostatic forces. In this manner, a lesser amount of paint is required to paint the product or vehicle, and the product or vehicle is painted more evenly and efficiently with less waste.
While this type of electrostatic painting process and/or system is effective to more efficiently and evenly paint a product or vehicle, it suffers from some drawbacks. For example and without limitation, oftentimes portions of the target product or vehicle become xe2x80x9cungroundedxe2x80x9d during the painting process. When this occurs, the product or vehicle will often exhibit non-uniform paint coverage and appearance and inferior quality. When non-conductive products or components are painted, robust grounding is even more critical, as the xe2x80x9cungroundingxe2x80x9d of a single part or portion of a component will cause surrounding parts to have poor paint coverage, thereby requiring the entire product or unit to be repainted.
Efforts have been made to detect the presence of an ungrounded condition in vehicles or products that are being electrostatically painted. For example and without limitation, visual inspections of the products or vehicle area typically performed during the painting process in order to ensure that the product or vehicle is sufficiently grounded. However, it is relatively difficult to visually detect or discern whether a portion of a product or vehicle becomes ungrounded after the painting process is completed. Particularly, these ungrounded conditions can typically be detected only after the product or vehicle has completed its cure cycle, when a film thickness is measured, or when a field failure (i.e., peeling) occurs due to thin film coverage. This xe2x80x9clatexe2x80x9d or xe2x80x9cdelayedxe2x80x9d detection requires the vehicle to be completely repainted, undesirably increases the cost and time required to complete the painting process, and decreases the efficiency of the overall painting process. Other attempts at detecting the xe2x80x9cungroundingxe2x80x9d of a portion or component of a vehicle include the use of conventional probes which are coupled to the vehicle. These probes, however, do not work on all types of products or vehicles and often provide inconsistent results.
There is therefore a need for an electrostatic painting system and method which is adapted for use in combination with a product or vehicle and which substantially ensures that the product or vehicle is sufficiently grounded during the painting process.
It is a first object of the invention to provide an electrostatic painting system and method which overcomes the drawbacks of prior systems and methods.
It is a second object of the invention to provide an electrostatic painting system and method which substantially ensures that a product or vehicle is sufficiently grounded prior to being painted.
It is a third object of the invention to provide an electrostatic painting system and method which utilizes an electrostatic volt meter to automatically identify ground failures in a product or vehicle before applying paint to the product or vehicle.
According to a first aspect of the present invention, a system for electrostatically painting a product is provided. The system includes a first station which selectively applies electrical charge to the product; a second station including at least one sensor which detects whether any portion of the product is electrically charged and which automatically generates a signal in response to the detection; and an electrostatic painting booth which selectively applies paint to the product. The system further includes a computer which is communicatively coupled to the at least one sensor and which is effective to receive the generated signal, the computer being further effective to selectively deactivate the painting booth based upon the received signal, thereby selectively preventing the product from being painted when any portion of the product is ungrounded.
According to a second aspect of the present invention, a method is provided for detecting ground failures in a product which is painted by an electrostatic painting process. The method includes the steps of: selectively applying an electrical charge to the product, effective to cause any ungrounded portion of the product to retain a residual voltage; and determining whether any portion of the product has a residual voltage, thereby detecting any ground failures within the product.
These and other objects, aspects, features, and advantages of the present invention will become apparent from a consideration of the following specification and the attached drawings.